1. Field of the Invention
The present invention generally relates to a cleaning composition, and more particularly to an acidic cleaning composition that is useful for removing the contaminants (such as abrasives, metal complexes, and organic compounds) from a wafer surface after a chemical mechanical polishing (CMP) process.
2. The Prior Arts
After copper deposition in the sub-micron copper (Cu) damascene procedure, the Cu-chemical mechanical polishing (Cu-CMP) process is performed in order to remove the excess Cu residing above the low-k dielectric layer and leaving the Cu inside the contact/via openings in the low-k dielectric layer.
In a chemical mechanical polishing process or a chemical mechanical planarization process, the wafer surface is mechanically polished for planarization by using a chemically reactive slurry. Slurries used in Cu-CMP process typically include 5 to 10 wt % of nano-abrasives (such as SiO2, Al2O3, CeO2, and ZrO2) with diameters of 30-100 nm; a chemical auxiliary agent (such as a pH buffer agent); an oxidizing agent (such as hydrogen peroxide, iron nitrate, and potassium iodate); a complexing agent; a corrosion inhibitor (such as benzotriazole (BTA)); and other compounds that act as protective film or act as surfactant. In the CMP process, the slurry is introduced to the wafer on a planarization table in conjunction with polishing pad, and the table and the wafer carrier are simultaneously rotated in order to polish the surface of the wafer. Consequently, a large amount of abrasives, metal, Cu-BTA complex compounds and other metallic and non-metallic contaminants will remain on the wafer surface after the CMP process. If the post-CMP cleaning solution used for removing the extrinsic contaminants left on the wafer surface after a CMP process is not effectively, the subsequent processes (such as thin layer deposition, photolithography, and etc.) will be detrimentally affected, and that will account for the enhanced degradation of device reliability.
In the conventional post-CMP cleaning process, the post-CMP cleaning solution which usually contains ammonium hydroxide was used together with the supersonic wave, spray, and brush devices in order to remove the contaminants from the wafer surface. The conventional post-CMP cleaning solution also usually included a surfactant which is also called a wetting agent that is able to lower the surface tension of the post-CMP cleaning solution, allowing easier spreading. However, the post-CMP cleaning solutions containing amines will smell very fishy, and the amines released from the cleaning solution can poison the photoresist stored in the wafer Fab and lead to reliability issues.
The cleaning compositions used after the CMP process have been described in prior art. The following are U.S. patents which describe such cleaning compositions: U.S. Pat. No. 7,208,049 disclosed a cleaning composition containing one or more surfactants that are used to reduce the number of defects in the manufacture of semiconductor devices. U.S. Pat. No. 6,627,546 disclosed a fluoride-free aqueous cleaning composition containing a dicarboxylic acid and/or salt thereof. U.S. Pat. No. 7,087,564 disclosed a cleaning composition containing ammonium citrate, and corrosion-inhibiting compounds (such as ascorbic acid, and cysteine).
There is still a need for a post-CMP cleaning composition for copper-containing wafer surface. Such a post-CMP cleaning composition should be able to effectively and efficiently remove the contaminants from the wafer surface while the roughness of the wafer surface only increases a little bit after such a post-CMP cleaning composition is used on a contaminated surface, so that the subsequent processes (such as thin layer deposition, photolithography, and etc.) can be favorably carried out.